A centrifugal compressor employs a wheel or impeller mounted on a rotatable shaft positioned within a stationary housing. The wheel defines a gas flow path from the entrance to the exit. A problem encountered with the operation of centrifugal compressors is the leakage of gas from the gas flow path before it completely traverses the gas flow path. This reduces the efficiency of the compressor.
Large diameter centrifugal compressors are used as feed compressors in the cryogenic air separation, non-cryogenic air separation, and process industries and they also are used as booster compressors at elevated inlet pressures in these and other processes. Large diameter impellers typically employ radial blades, i.e. are two dimensional arrangements. The problem of reduced operating efficiency is of particular concern with large diameter centrifugal compressors.